Device for the deflection of light beams

ABSTRACT

A device for deflecting light beams, in particular laser beams, has mirror surfaces which are arranged at a drivable rotating body. The rotating body is formed of monocrystalline material and the mirror surfaces are formed by the crystal planes and are arranged symmetrically with respect to rotation.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The invention is directed to a device for the deflection of light beams,preferably for deflection of laser beams, with mirror surfaces which arearranged at a drivable rotating body.

b) Description of the Related Art

For the purpose of deflecting laser beams which require a continuousbeam deflection for larger angles and a high deflecting speed, it isknown in the art to use polygon mirrors which are driven in rotation. Itis disadvantageous that the extremely complicated manufacture of thesemirrors results in extraordinarily high costs. Further, the tiltingfreedom of the individual mirror segments with respect to the axis ofrotation can not be ensured in the known polygon mirrors.

Further, deflecting mirror arrangements for light beams in which mirrorsurfaces which are suspended at torsional strips can tilt about therotational axis or in which the mirror surfaces are arranged at the endof movable tongue constructions are known from the field ofmicrotechnology. Electrostatic, piezoelectric or electrothermal driveswhich are generally functionally integrated with mechanics are used forsuch systems.

Although beam deflections of +/-10° can be realized by means of sucharrangements, the respective mirror surfaces can only be produced in therange of 50×50 μm² to 500×500 μm ². In known systems, the dynamicresponse has proven very problematic. At high frequencies, theattainable deflecting angle decreases drastically since the forcesrequired for accelerated movement of the mirror surfaces can no longerbe applied using the selected drive principles. Moreover, there occurvibration modes which result in a warping of the mirror surfaces. Inorder to enable a more reliable movement of the mirror surfaces also athigher frequencies, their mass must be drastically reduced, which isonly possible in existing mirror surfaces by reducing their thickness.However, this leads to increased development of vibrations on the mirrorsurface and accordingly to operating disturbances.

OBJECT AND SUMMARY OF THE INVENTION

The summary object of the present invention is to provide a beamdeflecting system which enables a high deflecting frequency at largedeflecting angles and for large mirror surfaces, ensures a tiltingfreedom of the individual segments with respect to the rotational axisand can be manufactured economically.

This object is met according to the invention for the deflection oflight beams including the deflection of laser beams. The devicecomprises a drivable rotating body. Mirror surfaces are arranged at thedrivable rotating body. The rotating body is formed of microcrystallinematerial. The mirror surfaces are formed by crystal planes of themicrocrystalline material and are arranged so as to be symmetric withrespect to rotation.

The arrangement according to the invention is characterized inparticular by the following advantages:

realization of high deflection frequencies also for relatively largelight beam diameters;

economical mass production, since the advantageous techniques of batchprocessing in microelectronics can be used in micromechanics;

tilting freedom of the segments relative to one another;

high reflecting capacity of the mirror surfaces due to the providedmaterials.

The invention is explained more fully in the following with reference toembodiment examples.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIGS. 1 and 2 show a device according to the invention in which themirror surfaces are located in a depression on the rotating body; and

FIGS. 3 and 4 show a device according to the invention in which themirror surfaces are located at a mesa structure arranged on the rotatingbody.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the arrangement shown in FIGS. 1 and 2, the base body 1 contains acut out portion 11 whose dimensions are greater than those of thedisk-shaped rotating body 2. The rotating body 2 is formed of amonocrystalline material, preferably silicon, and contains a centrallyarranged polygonal depression 21. The depression 21 is defined laterallyby crystal planes of the rotating body 2 forming the mirror surfaces 22.An annular, segmented hard-magnetic layer 23 whose center defines therotational axis of the rotating body 2 is located on the upper side ofthe rotating body 2. The base body 1, within whose cut out portion 11the rotating body 2 is located, is hermetically sealed at the upper sideby a cover plate 3 of glass. A toroidal magnet 4 and a quantity of coilpairs 31 with integrated flux guide pieces 32 are located on this coverplate. An opposite-pole magnet 5 is arranged at the underside of thebase body.

FIGS. 3 and 4 show another embodiment form of the device according tothe invention in which a polyhedral mesa structure 24 is centrallyarranged on the disk-shaped rotating body 2. The mesa structure 24 isdefined laterally by crystal planes of the rotating body 2 which formthe mirror surfaces 22. Hard magnets 23 whose center defines therotational axis of the rotating body 2 are disposed annularly on theupper side of the rotating body 2. The base body 1, within whose cut outportion 11 the rotating body 2 is located, is again hermetically sealedat the upper side by a cover plate 3.

In both constructions, the rotating body 2 is held so as to be suspendedin the cut out portion of the base body 1 by means of the segments ofthe hard-magnetic material on its upper side, by the force of thetoroidal magnet 4 and opposite-pole magnet 5 and by the magnetic fieldof the coils 31. Due to the annular construction of the magnet, therotating body 2 is centered in a compulsory manner. By suitablycontrolling the coil pairs 31 arranged on the base body 1, a magneticfield is generated along the flux conducting layers 32, this magneticfield in cooperation with the hard-magnetic segments on the rotatingbody 2 causing a turning moment. Accordingly, with a multi-polararrangement, the rotating body 2 can be set in rotation withoutwobbling.

A light beam striking a mirror surface 22 of the rotating body 2 can bedeflected by an angle of up to roughly 60° by the rotating movement ofthe mirror surface about the axis of rotation. The device according tothe invention enables very high rotating speeds because, as a result ofthe self-centering magnet bearing, effects of friction are almosttotally eliminated and unbalance can be minimized.

While the foregoing description and drawings represent the preferredembodiments of the present invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the true spirit and scope of the presentinvention.

What is claimed is:
 1. A device for deflecting optical beams includinglaser beams, comprising:a base body having a recess; a disk-shapedrotating body disposed in said recess, said rotating body having mirrorsurfaces disposed in a rotationally symmetric arrangement; a cover plateattached to said base body to close said recess; a plurality ofhard-magnetic segments located in an annular arrangement on an uppersurface of said rotating body, said annular arrangement having a centercoinciding with an axis of rotation of said rotating body; at least onering magnet located on said cover plate; an opposite-pole magnetarranged on said base body below said rotating body; and a plurality ofelectromagnet coils arranged on said cover plate for generating amagnetic field to exert a torque on said rotating body in cooperationwith a magnetic field of said hard-magnetic segments and to hold saidrotating body in a freely floating manner in said recess in cooperationwith a field of said ring magnet and a field of said opposite-polemagnet.
 2. The device defined in claim 1 wherein said rotating body ismade of monocrystalline material.
 3. The device defined in claim 2wherein said rotating body has a central depression in which said mirrorsurfaces are located.
 4. The device defined in claim 3 wherein saidmonocrystalline material has defined crystal planes with an angle ofinclination, said depression having a polygonal cross-section, saidmirror surfaces extending at said angle of inclination.
 5. The devicedefined in claim 2 wherein said rotating body includes a polyhedral mesastructure, said mirror surfaces being side surfaces of said mesastructure.
 6. The device defined in claim 1 wherein said rotating bodyhas a central depression in which said mirror surfaces are located. 7.The device defined in claim 1 wherein said coils are provided withintegrated flux conductors.
 8. The device defined in claim 1 whereinsaid cover plate closes said recess in a hermetic seal.